JP3847627B2 - Digital hearing aid with voltage converter - Google Patents

Abstract

A digital hearing aid comprises a microphone (2), an output transducer (3), a digital signal processor (5) interconnected between the microphone and the output transducer, and a power source (7) including a standard hearing aid battery for the supply of operation voltage for the digital signal processor. At least one of the integrated circuit signal processing parts is designed to operate at a reduced unstabilized operation voltage substantially below a nominal voltage of the battery. A switched step-down voltage converter is connected between the power source and such signal processing parts for lowering the battery voltage to provide the reduced operation voltage.

Description

[0001]
The present invention includes a microphone, an output converter, a digital signal processor interconnected to and between the microphone and the output converter and including one or more integrated circuit signal processing parts, and the signal processing part And a power supply including a standard hearing aid battery for supplying an operating voltage to each of the digital hearing aids.
[0002]
In the new state, a normal hearing aid battery supplies a voltage of about 1.3V, and during its operating life, the hearing aid battery supplies enough current for the operation of the hearing aid until it drops to a voltage of about 1V. When the voltage is lower than that, the power supply capacity of the hearing aid battery is rapidly reduced.
[0003]
In the prior art for hearing aids, for example, according to EP-A-0 335 542, US-A-4,539,440, US-A-5,581,455, a voltage step-up converter is used to configure a certain processing circuit or EEPROM memory or microphone circuit. It is well known to provide an element with an operating voltage that is higher than the normal (nominal) battery voltage. In many cases, the voltage step-up converter takes the form of a switched capacitor network designed, for example, as a so-called charge pump voltage multiplier.
[0004]
Further examples of the use of voltage limiters in hearing aids are disclosed, for example, in DE-A-27 38 339, DE-C-3134 888, DE-A-197 02 151, WO-A-96 / 03848. Outside the field of hearing aids, a voltage drop circuit using low power consumption MOSFET technology is disclosed in US-A-4,205,369.
[0005]
In conventional hearing aid technology, most of the power supplied is required to provide a high enough operating voltage to operate the signal processing circuit, and the voltage reduced from the nominal battery voltage is voltage stable. It is used only to provide a reference voltage. Further reduction in operating voltage has been considered inconvenient because it results in a reduction in processing speed. In certain parts of a digital hearing aid, such as a D / D output converter, which is a major part of power consumption, reducing the operating voltage will only increase the current and reduce the output power consumption from the D / D converter. I can't save.
[0006]
Furthermore, in a small hearing aid that operates with only a few mA or a very small mA drain current with a low voltage drop, a circuit configuration of a low-loss and stabilized series voltage regulator when trying to save power by reducing the operating voltage. It was not of interest because the elements were complicated.
[0007]
As long as the operating voltage is kept higher than the defined minimum voltage, the invention makes it possible for an integrated circuit signal processing part of a digital hearing aid, e.g. a digital filter, to not cause a significant change in performance due to a change in operating voltage, i.e. operation. This is based on the fact that the sensitivity to voltage changes is low.
[0008]
Therefore, an object of the present invention is to provide a digital hearing aid that has a longer operating battery life and lower power consumption.
[0009]
According to the present invention, this and other objects are designed such that at least one of the integrated circuit signal processing units is designed to operate at a reduced operating voltage sufficiently lower than the nominal voltage of the battery. A switch step down voltage converter for supplying a voltage is achieved by a digital hearing aid, characterized in that it is connected between the power source and the at least one signal processing unit to which a reduced battery voltage is applied. The
[0010]
By reducing the operating voltage required for operation of the integrated signal processing circuit portion, the total drain current and power consumption of the hearing aid is reduced. This provides significant advantages in terms of power consumption, particularly in digital signal processing operations that can consume significant power, operating with programs programmed with large hardware.
[0011]
Preferably, the digital signal processor with a reduced required operating voltage uses MOS or CMOS technology, for example a low threshold or pinch-off voltage compared to a bipolar processing circuit normally used in hearing aids. Designed using voltage transistors. Typically, such a signal processor is a circuit that does not focus on processing speed or required output power, such as a digital filter circuit. On the other hand, higher operating voltages are still supplied to circuits that focus more on processing speed or required output power, such as output D / D converters or output amplifiers.
[0012]
For example, the proper design of signal processing blocks, including branches to many parallel or serial processing blocks, will focus on processing speed requirements and reduce operating voltage requirements by such circuit blocks. Is done.
[0013]
Therefore, in a preferred embodiment of the hearing aid according to the present invention, the one or more signal processing units are realized by parallel signal processing blocks each operating at a reduced operating voltage. The reduced operating voltage for the signal processor in question is equal to or lower than 0.8V, such as 0.7-0.4V, or preferably 0.65 to 0.5V, of nominal battery voltage. It is preferably within half the voltage range.
[0014]
In a preferred embodiment, the switch step-down voltage converter that provides the reduced operating voltage is a capacitive charge pump converter, which is beneficially designed to output two or more output voltages. Alternatively, a switch inductor type converter may be used.
[0015]
Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.
[0016]
The hearing aid schematically shown in FIG. 1 comprises a microphone 2, an output transducer or receiver 3, and an electrical circuit 1 connected between them. The electric circuit 1 includes a signal processing unit 5, a control unit 6, and a power supply unit 7. In the digital hearing aid, the signal processing unit 5 includes at least an A / D converter and a digital signal processing circuit for converting an analog signal from the microphone 2 into a digital format. The digital signal processing circuit includes a filter, an amplifier, and an output converter, and a digital or analog output signal that compensates for the hearing loss of the user is supplied to the output converter 3 by the output converter.
[0017]
The charge pump type switch-capacitor voltage step-down converter shown in FIG. 2 is disclosed in US-A-4,205,369, and is a voltage like a hearing aid battery that provides a nominal voltage U _cc of about 1.3V. It is connected to a source DC series, and a converter configuration supplying about one-half of the output voltage xU _out of nominal voltage. The converter circuit comprises a pair of transistors T1, T2 which are shown as p-type and n-type MOSFET transistors, respectively. The converter circuit is controlled by a control voltage v, is connected to the switch circuits S1 and S2, and is realized as a pair of n-type and p-type MOSFET transistors controlled by opposing clock phases.
[0018]
The transistors T1 and T2 and the switch circuits S1 and S2 control charging and discharging of the two capacitors C _f and C _s as follows.
[0019]
When the control voltage v is non-dynamic or “low”, the transistor T1 is turned on, the transistor T2 is turned off, the switch circuit S1 is not activated, and the switch circuit S2 is activated. Therefore, as shown in the equivalent diagram of FIG. The capacitors C _f and C _s are connected in series and charged.
[0020]
When the control voltage v is dynamic or “high”, the transistor T1 is off, the transistor T2 is on, the switch circuit S1 is activated, and the switch circuit S2 is not activated, as shown in the equivalent diagram of FIG. Capacitors C _f and C _s are parallel to the load and discharged. 3 and 4, the load is indicated by a resistor R1.
[0021]
If the capacitors C _f and C _{s have} the same capacitance, the battery voltage U _cc is divided in half, and the reduced supply voltage xU _out is about half of the battery voltage.
[0022]
In the form shown in FIG. 5, the three MOSFET transistors T1, T2, and T3 and the four switch circuits S1, S2, S3, and S4 have three capacitors C _f , C _f2 , C _{s in the} same manner as described above. Connected to control charging and discharging.
[0023]
When the control voltage v is “low”, the transistors T1 and T3 are on, the transistor T2 is off, the switch circuits S2 and S4 are activated, and the switch circuits S1 and S3 are not activated. In this way, the capacitor C _s is charged in series with the capacitors C _f and C _f2 connected in parallel.
[0024]
When the control voltage v is “high”, the transistors T1 and T3 are off, the transistor T2 is on, the switch circuits S2 and S4 are not activated, and the switch circuits S1 and S3 are activated. As shown, capacitors C _f and C _f2 connected in series are in parallel with a capacitor C _s and a resistor R 1 in parallel with the capacitor C _s and are discharged.
[0025]
If the capacitances of capacitors C _f , C _f2 and C _s are equal, battery voltage U _cc is divided by 3 and the reduced supply voltage xU _out is about 2/3 of the battery voltage.
[0026]
The configurations shown in FIGS. 3 and 6 are merely illustrative of a preferred embodiment of a switched-capacitor charge pump converter for use with the digital hearing aid of the present invention. Within the scope of the present invention, one or more reduced operating voltages for the various signal processors in the hearing aid are obtained by part of the battery voltage.
[0027]
Continuing from the above description, the reduced operating voltage supplied by the voltage step-down converter of the present invention is not initially stabilized, resulting in a change in battery voltage. However, it will be apparent to those skilled in the art that, if necessary, the advantages of low power consumption according to the present invention can be maintained by generating a stable low voltage with a conventional regulated voltage regulator.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing an embodiment of a digital hearing aid according to the present invention.
2 shows a first form of a charge-pump type switch-capacitor voltage step-down converter used in the hearing aid of FIG. 1. FIG.
FIG. 3 is a simplified diagram showing the state of charge in the converter configuration of FIG. 2;
4 is a simplified diagram showing the state of charge in the converter configuration of FIG. 2;
5 shows a second form of a charge-pump type switch-capacitor voltage step-down converter used in the hearing aid of FIG. 1. FIG.
6 is a simplified diagram showing the state of charge in the converter configuration of FIG. 2;
7 is a simplified diagram showing the state of charge in the converter configuration of FIG. 2;

Claims (8)

A microphone (2), an output converter (3), a digital signal processor (5) connected between the microphone (2) and the output converter (3), and the digital signal processor A digital hearing aid having a power supply (7) including a standard hearing aid battery for supplying an operating voltage to
The digital signal processor is at least one integrated circuit signal that is operable within a reduced operating voltage range that is sufficiently lower than a nominal voltage of the battery and higher than a defined minimum voltage that does not cause a significant change in performance. Including a processing unit,
A digital hearing aid, wherein a switch step-down voltage converter is connected between the power source and the at least one signal processing unit to which a reduced power source voltage is applied.   The digital hearing aid according to claim 1, wherein the at least one signal processing unit is designed using CMOS technology.   The digital hearing aid according to claim 1 or 2, wherein the at least one signal processing unit is configured by parallel signal processing blocks each operating with a reduced power supply voltage.   4. A digital hearing aid according to claim 1, 2 or 3, characterized in that the reduced power supply voltage is equal to or lower than 0.8 volts.   5. A digital hearing aid according to claim 1, wherein the converter is a capacitive charge pump converter.   6. A digital hearing aid according to claim 5, wherein the charge pump converter is designed to output two or more output voltages, at least one of which is the reduced power supply voltage. .   The digital hearing aid according to any one of claims 1 to 4, wherein the voltage converter is a switch-inductor-network converter.   The digital hearing aid according to any one of claims 1 to 7, wherein the reduced power supply voltage is an unstabilized voltage.

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